CVE-2026-42051: Kirby is an open-source content management system

Routine

MEDIUM 4.3UPGRADE

CVE-2026-42051 is a medium-severity flaw (CVSS 4.3) affecting kirby. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Kirby is an open-source content management system. Prior to versions 4.9.0 and 5.4.0, the system API endpoint leaks license data and installed version to authenticated users. This issue has been patched in versions 4.9.0 and 5.4.0.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.2% (top 91%)
CISA exploited list	No
Weakness	CWE-862
Published	2026-05-09
Last modified	2026-07-24

Publisher (CNA): GitHub, Inc. · Vendor: getkirby

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-09 04:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

getkirby kirby UPGRADE

Affected: < 4.9.0 · >= 5.0.0 and < 5.4.0

Fixed in: 4.9.0, 5.4.0

Safe to downgrade to: a release before 5.0.0

1. Check installed version

apt-cache policy kirby || rpm -q kirby || kirby --version

2. UPGRADE to 4.9.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade kirby

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade kirby

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.0.0 (Debian / Ubuntu)

apt-cache madison kirby sudo apt install kirby=<VERSION_BEFORE_5.0.0> sudo apt-mark hold kirby

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list kirby sudo dnf downgrade kirby-<VERSION_BEFORE_5.0.0> sudo dnf versionlock add kirby

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42051?

kirby: upgrade to 4.9.0, 5.4.0. Exact commands for each OS are on this page.

Is CVE-2026-42051 being exploited?

CVE-2026-42051 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42051 affect?

CVE-2026-42051 affects kirby. Severity is medium (CVSS 4.3). Kirby is an open-source content management system. Prior to versions 4.9.0 and 5.4.0, the system API endpoint leaks license data and installed version to authenticated users. This issue has been patched in versions 4.9.0 and 5.4.0.

How urgent is CVE-2026-42051?

Priority 17/100. No elevated risk signals yet.

Related CVEs

CVE-2026-32870 HIGH 7.5 UPGRADE Kirby is an open-source content management system
CVE-2026-41325 HIGH 8.8 UPGRADE Kirby is an open-source content management system
CVE-2026-40099 MEDIUM 6.5 UPGRADE Kirby is an open-source content management system
CVE-2026-34587 HIGH 8.1 UPGRADE Kirby is an open-source content management system
CVE-2026-42069 MEDIUM 6.5 UPGRADE Kirby is an open-source content management system

References

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